ecology test 3 (copy)

life table

age or stage specific account for mortality

cohort

group of individuals born in the same period of time

nx

abundance at age X

dx

individuals dying between stages
nx-(nx+1)

lx

survivorship (probability)
Nx/N0

qx

mortality rate
dx/nx

type 1 survivorship curve

low death rates during early and middle life and an increase in death rates among older age groups
-humans many mammals

type 2 survivorship curve

fairly constant death rate at all ages
-birds, rodents, reptiles, perennial plants

type 3 survivorship curve

a pattern of survival over time in which there is low survivorship early in life with few individuals reaching adulthood
-fish, inverts, many plants

fecundity

rate of production of young by females

bx

average number of female offspring produced by an individual at age x

lxbx

mean number of females born in each age group, adjusted for survivorship

R0

Lxbx added across all age groups,
R0>1= population is growing
R0

exponential population growth

Nt+1=Nt+(births-deaths)
dN/dT-rNt
r= instantaneous per capita rate of growth

influence on birth rates

-natality: number of young per breeding attempt
-age at sexual maturity
-reproductive span:# of breeding years
-interbirth interval
-age of female
-nutritional state of females

maximum rate of growth

is determined by a species life history
(Births-deaths)

sx

the survival rate from one age class to the next age class
sx=1-qx
-can be used to project population growth

age distribution

The proportion of individuals of different ages within a population

Projecting population growth

N(t+1)=N(t)λt
λ>1: increasing population
λ

logistic growth

dN/dt=rN(1-N/K)
-rate of population growth maximized halfway to carrying capacity

density dependent factors affecting population dynamics

-environmental factor whose effects on a population change as the population density changes
-growth declines as N increases (usually)
-density dependent mortality
-density dependent fecundity

density independent factors affecting population dynamics

-environmental factor that affects the size of a population but is not influenced by changes in density
-ex. weather events, pollutants

competition

-interaction among individuals where both attempt to use a common essential resource; mutually detrimental to both participants
-intraspecific (individuals of same species)
-interspecific (individuals of different species)

individuals compete for

food, space (enemy free space), light, water

scramble competition

growth and reproduction are depressed equally across individuals in a population as the resource declines
-herbivores and available forage (exploitation)

contest competition

some individuals control sufficient resources while others in the population suffer
-carnivores and prey base (interference)

effects of intraspecific competition

-increased stress
-slowed growth and development
-reduced reproduction

Territoriality

Defense of a space against encroachment by other individuals

demographic stochasticity

random variation in birth and death rates from year to year

environmental stochasticity

variation in environmental conditions can greatly affect birth and death rates

deterministic population model

-birth and death rates assumed constant
-use averages to incorporate range of possible outcomes

stochastic models

-incorporate probability
-use simulations to get a range of potential outcomes

landscape ecologists

-study the structure, function, and/or changes of a landscape
-they study how the characteristics of a landscape influence: dispersal, disease, propagation, energy flow, etc.
-they focus on spatial heterogeneity and detecting patterns at large scales

populations are spatially structured

-not found in an uniform way
-elevation determined big horned sheep populations
-demonstrates metapopulations

metapopulation

a network of subpopulations linked by individual movements
-populations are equivalent and extinction of local populations is stochastic (random) event

subpopulations

local populations determined by distribution of patches of suitable habitat

Abiotic landscapes

a non-living part of an ecosystem that shapes its environment

Biotic landscape

a living organism that shapes its environment

anthropogenic

Human-induced changes on the natural environment

patch

area that is more homogenous than surroundings

matrix

dominant community in an area

boundary

location where patches meet

characterization of boundaries

-narrow border (abrupt boundary)
-wide border (ecotone)
-convoluted border (wavy)
-perforated border

ecotone

The transition from one type of habitat or ecosystem to another, such as the transition from a forest to a grassland
-often contain high biological diversity
-contain patch species, matrix species, edge species

fragmentation

degree of patch (dis)continuity

size of patch

increased size of patch= increased area= increased species able to be supported

shape of patch

more regular shape, less "edge"
-species that are edge species, interior species, and area-insensitive species

corridors

relatively linear areas of habitat that connect patches
-increase connectivity in patches
-increases colonization rates

connectivity

the degree to which patches interact with one another

connecivity

structural and functional

island biogeography theory

A theory that was initially applied to oceanic islands to explain how species come to be distributed among them. Aspects of the theory include immigration and extinction rates,island size, and distance from the mainland.

Single Large or Several Small (SLOSS)

-refers to two different approaches to land conservation in order to protect biodiversity in a given region.
-The "single large" approach favors one sizeable, contiguous land reserve.
-The "several small" approach favors multiple smaller reserves of land whose total areas equal that of a large reserve.

population growth affected by

births, deaths, immigration, emigration

metapopulation dynamics-genetics

local dynamics, landscape dynamics

metapopulation persistence

determined by local extinction and recolonization of subpopulations

source-sink theory

-assumes habitat quality varies from patch to patch
-models population dynamics in the context of heterogeneous habitats patches
-variation in habitat quality affects demographic rates (birth/death)
-there are intrinsic differences in habitat quality, so without immigration extinction in the sink is deterministic

source

-good quality
-natality> mortality
-r>0
-demographic excess
-net emigration

sink

-lower quality
-mortality> natality
-r

metapopulation dynamics

patch size, isolation, and location are not static (change over time due to environment)
-within-species interactions

metacommunity dynamics

between-species interactions

interspecific competition

-an interaction that negatively affects two or more species
-cornerstone of evolutionary ecology- the motivation for darwin's theory of natural selection
-driving force behind species divergence and phenotypic specialization

mechanisms of competition

-exploitation
-interference

more specifically:
1. consumption
2. preemption
3. overgrowth
4. chemical interactions
5. territoriality
6. encounter

consumption competition (food exploitation)

when an individual of one species inhibits the growth of an individual of another species by consuming a shared resource

pre-emptive competition (space interference)

when an individual of one species occupies a given area and thereby precludes the establishment by others
-occurs primarily in sessile species

overgrowth competition (light interference)

when one organism grows over top of another organism and prevents access to essential resources

chemical interactions

growth inhibitors or toxins released by one species inhibits growth or kills another
ex. allelopathy in spotted knapweed

territorial competition (space interference)

the behavioral exclusion of other species form space that is defended as a territory

encounter competition

when non-territorial meetings between individuals negatively affects one or both participating species

Lotka-Volterra Model

A continuous-time model that calculates the influence of each of two populations (predator and prey, or competitors) on the abundance of the other

four possible outcomes of interspecific competition

1. species 1 wins
2. species 2 wins
3. each species could outcompete each other
4. neither species can achieve the necessary density to out compete the other (coexistence)

the competitive exclusion principle

two species that live in the same place and have the same ecological requirements cannot coexist

assumptions of the competitive exclusion principle

1. Competitors have exactly the same resource requirement
2. Environmental conditions remain constant (rare)

factors that affect competition

-rapid growth increases a plant's ability to compete for space, nutrients in light
-however, non-resource factors also affect growth and germination (pH, temperature, relative humidity, salinity)
-temporal variation in the environment
-competitive ability varies with environmental gradients
-superior competitor depends on nutrient availability

ecological niche

sum of a species' tolerance limits for all environmental factors

niche

consists of all the factors necessary for a species' existence in terms of time, space, and required resources

fundamental niche

all the possible dimensions in which species can survive

realized niche

the dimensions a species occupies after the effects of interspecific competition and other biotic interactions

species one wins

species 2 wins

competition can go either way

outcome 4: coexistence

evolutionary response to competition

-competitive interactions among species are not stable over evolutionary timescales
-populations should evolve to reduce negative effects of competition by minimizing interaction
-competition promotes the evolutionary divergence of tolerance ranges

character displacement

when tolerance ranges differentiate to reduce interaction
ex. there is an overlap in beak size for Galapagos ground finches but in islands where they are together, there is no overlap in beak size

resource partitioning

when two or more organisms use different portions of a common resource simultaneously
-ex. resource partitioning in prairie plants reduces competition for soil moisture

how different do species need to be?

-often species are competing for multiple resources
-multidimensional nature of resource requirements reduces niche overlap

competition interacts with environmental factors

degree to which competition shapes communities varies along environmental gradients
-ex. one side of scale is community shaped by stress tolerance vs. other side is community shaped by competition for nutrients

disassociated injurious feeder

-interaction doesn't last long, prey isn't killed
-"grazer like"
-ex. rabbits eating plants

intimate injurious feeder

-interaction is long lasting, prey not killed
-"parasite-like"
-ex. parasite on host

intimate lethal feeder

-interaction is long lasting, prey killed
-"parasitoid-like"

disassociated lethal feeder

-interaction doesn't last long, prey killed
-"predator like"
-ex. lion and antelope

Predator population equation

prey zero growth isocline

-predator density zero/low, exponential growth
-predator density increases; at some point mortality=births

predator zero growth isocline

-prey density zero/low, predator population declines from low birth rate
-growth rate of predator is zero when rate of increase (from consuming prey)= rate of mortality

oscillations of prey vs. predator population

-populations oscillate/cycle out of phase
-predator population lags behind prey

numerical response

increase in predator population associated with increased consumption of prey

processes of numerical response of predators

1. increased reproduction as rate of prey consumption increases
2. aggregative response as predators move into areas of high prey density

functional response

change in per capita rate of consumption as the number of prey fluctuates

functional response curves

describe the per capita rate of consumption for a predator relative to the number of prey available

classification of functional response curves

-for a predator, time spent foraging is divided into searching time and handling
-allocation of resources to each time component, in part dictates the type of functional response

type 1 functional response

rate of predation is constant
-passive predators (spiders, aquatic filter feeders)